Automatic telephone system



Sept 15, 1925.

J. ERICKSON *AUTOMATIVC TELEPHONE SYSTEM Filed Nov. 17, 1920 2 Sheets-Sheet l Sept. 15, 1925.

J. ERICKSON AUTOMATIC TELEPHONE SYSTEM Patented Sept. 15, 1925.

A 1,553,935 UNITED STATES-PATENT OFFICE.

JOHN ERICKSON, OF CHICAGO, ILLINOIS, ASSIGN'OR TO AUTOMATIC ELEGTRIC OOM- PANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Application filed November 17, 1920. Serial No. 424,752.

To all whom it may concern:

Be it known that I, JOHN ERICKSON, a citizen of the United States of America, and a resident of Chicago, Cook County, and State of Illinois, have invented certain new -and useful Improvements in Automatic Telephone Systems, of which the following is a specification.

The present invention relates in general to automatic .telephone systems, but more particularly to such automatic systems as include two or more different oflices or exchanges; and the object of the invention, broadly stated, is to provide new and improved trunk circuits for connecting two automatic exchanges whereby a plurality of small and inefiicient groups of trunk lines may be combined into one large and more efficient group.

The idea involved is not entirely new, and reference is made at this time to the Martin Patent No. 1,435,249, issued Nov. 14, 1922, which discloses suitable means for accomplishing the desired result. New circuits have been designed, however, operating on new principles, whereby the required selective operations are controlled in a more satisfactory manner, and a trunking system is thus provided which is more economical to install, and is more satisfactory in practical operation. These improvements will be fully described hereinafter with reference to the accompanying drawings, in which sufficient of the apparatus of an automatic telephone system is illustrated by means of the usual circuit diagram to enable the invention to be explained and understood.

Referring to the drawings, comprising Figs. 1 and 2, the reference characters 95 and 96 indicate the two conductors of a trunk line connecting two exchanges and extending from the repeater D in the first exchange to a group of relays F in the second exchange. This trunk line is-one of a relatively large group of trunk lines formed by combining four small groups, and each trunk line in the group thus formed isaccordingly rendered accessible from four different selector levels in the first exchange. The arrangement is clearly illustrated in Fig. 1 of the drawings, Where it will be seen that the repeater D may be reached by way of any one of the four sets of bank contacts at the left of the sheet.

Atthe distant exchange each trunk line has four branches which may terminate in selector switches, or other types of switching mechanism, depending on circumstances. In the case of the trunk line shown, the four branches are associated with relays 101, 102, 103, and 104, respectively, and each of these relays is adapted, when energized, to connect the trunk line with its associated branch. In the operation of the system in setting up inter-exchange connections, the several branches are separately connected to the trunk line in question in accordance with the different selector levels at which the trunk lineis taken for use in the first exchange; that is, if the trunk line is connected with by way of the first level, the first branch will be connected up, if seized from the second level the second branch will be connected up, and so on. The relays in the relay group F have the function of selectively connecting the several branches in the manner set forth and are controlled by characteristic. circuit conditions impressed on the conductors of the trunk line by the relays in the relay group E, Fig. 1.

As intimated herein before, the new circuit arrangements for controlling the branch connecting relays form the principal subject matter of the invention, and the selecting operations involved will now be explained more in detail, it being assumed for this purpose that a subscriber in the first exchange, which may be considered to be a branch exchange, desires to obtain a connection with a subscriber in the second exchange. For convenience it is assumed furthermore that the telephone number of the desired station in the second exchange is #4567.

WVhen the calling subscriber removes his receiver to initiate the call, a line switch, individual to the calling subscribers line, operates in the well known manner to extend the line to an idle first selector. The selector in response to the calling of the first digit 4 of the desired number, raises its wipers to the fourth level and rotates them to pickout an idle trunk. We will assume that the trunk line terminating in bank contracts 11, 12, and 13, Fig. 1, is the one which is seized.- When the selector seizes the trunk it immediately sends out a guarding ground over its private wiper to prevent the seizure of this trunk by any other switch. This ground, in addition to guarding the seized relay set E over t I armature 39 and its resting contact, armature 38 and its resting contact, armature 37 and its resting contact and through relay 64 to battery. Relay 64, upon energizing, ex-

tends the guarding ground through arma ture 36 and its Working contact to test contacts 3, 6, and 9. When the selector cuts the calling line through to the repeaterD a circuit is closed for the line or repeating relay 30 of the repeater D over the two SideS Of the calling line in series. The relay 30, upon through armature 70 and its working contact, armature 69 and its resting contact, upper w1nd1n of relay 31, normally closed contact contro led by armature 78, conductor of this bridge across the trunk conductors .95 and 96 completes the following circuit:

from ground through the lower;w1nding of line relay 150 otthe selector H, Fig. 2, by way of the'resting contact of armature 177 and said armature, conductor 182, working energizing, closes a circuit from ground eontact of armature 132 and said armature,

at test contact 12, and also closes a circuit for the lower winding of rela 31in paral-' 'lel with relay 35 to battery. elay 35 energizes over this circuit but relay31 does not energize on account of the high resistance and small number of turns 0 said lower winding. 'However, before the relay 35 has had time to energize, the previously mentioned energization of relay 64 has closeda circuit from battery through the resistance Rinthe relay set E, armature 84 and its working contact, resting contact of armature 74 and said armature, conductor 96, armature 129 and its resting contact, armature 130 and its resting contact, armature 131 and its resting contact, armature 132 and its resting contact and thence through normal ly operated relay 107 to ground. The -com-' relays 112 and 104, respectively. 7 Relay 112,-

being wound with. fewer turns, energizes first and at its armature 124 closes the cir cuitof relay 104 at another point. Upon energizing, relay 104 disconnects the trunk line conductors 95 and 96 from their normal connections in the relay group F by means of its armatures 128 and 132, and extends them at the working contactsof thesearmatures to conductors 180 and 182, respectively, of the branch trunk line extendin to the selector H. This operation opens t e shunt that was closed around relay 108, which causes it to operate and break the circuit for relay 112,which later falls back and opens the circuit at armature 124 for relay 104.

Before relay 104 has had time to fall back,

traced bridge through repeater D, armature 75, conductor 95, normally closed contacts at armatures 125, 126, and 127, armature 128 and its working contact, conductor 180, armature 176 and its resting contact, and upper winding of line relay 150 to battery. I The line relay 150 of selector H accordingly energizes over this circuit and closes a circu1t for the release relay 151. The latter relay, upon energizing, prepares the vertical magnet circuit and also grounds the release trunk conductor 181, which supplies holding ground. to relay 104 before said relay has had time to deenergize. The relay 31 at the repeater D does not energize in series with relay150, as the current flowing in its upper winding opposes that flowingin its lower winding. The trunk line is now entirely disconnected from relay sets E and F and is ready for the usual impulses.

The calling subscriber now operates his callin device in accordance with the second digit 5 ofthe desired number. Five interruptions are thus produced in the line circuit andat each interruption the repeating relay 30 falls back and closes a circuit for relay 32, extending from ground through armature 65 and its resting contact, armature 73 and its working contact, and relay 32 to battery. Relay 32 energizes over this circuit and being slowacting maintains its armature attracted during the operation. The relay 32, upon energizing, opens the before mentioned bridge for conductors 95 and 96 and closes the same over a direct path extending through armature 69 and its working contact, conductor 98, working contact of armature 79' and said armature, and over conductor 100 to the working contact of armature 74. Each time the repeating relay 30 falls back it opens this direct bridge and thus interrupts the circuit of the line relay 150 of selector H. The said line, therefore, deenergizes a plurality of times and sends a series of. impulses from ground through theslow acting relay 152 in series with the vertical-magnet 157 to battery. By

the operation of the vertical magnet the sethe shaft, and upon the closure of the vertical ofi' normal springs 189 completes a circuit for the step-ping relay 153. Upon energizing, relay 153 prepares a circuit for the rotary magnet 156 at its aramture 191 and at armature 190 establishes a locking circuit for itself. At the end of the vertical operation of the switch the slow act-ing relay 152 is deenergized and closes the circuit of the rotary magnet, which thereupon energizes to advance the wipers 161-163, inclusive, into engagement with the first set of bank contacts in the level opposite which they were raised. The rotary magnet also breaks the circuit of the stepping relay 153 which deenergizes and breaks the circuit of the rotary magnet, which thereupon deenergizes also and again closes its interrupter contact. The operation now depends upon whether the test contact with which test wiper 162 is in engagement is busy or is not busy. If the test contact is busy it will have a ground potential on it, and the stepping relay 153 will energize again and the same cycle of operations will be repeated until an idle or ungrounded contact is reached, when the switching relay 154 will energize in series with the stepping relay over the following circuit: from grounded conductor 181 through relay 154, interrupter contacts of the rotary magnet 156, off normal springs 189 and relay 153 to battery. Relay 153, however, due to its relatively small number of turns, does not energize over this circuit. Ve will assume that test contact 165 is the first one found idle, in which case the energization of relay 154 will switch the connection through to the trunk line comprising conductors 167, 168, and 169, which lead to a connector switch. Before the release relay 151 has had time to fall back and take ground off the release trunk conductor 181, the line and release relays of the connector ahead pull up in the well known manner to ground the release trunk conductor 168, thereby establishing a holding circuit for the switching relay 154 of the selector H and for the relay 104;

The next digit 6 raises the connector wipers. until they stand opposite the sixth level of bank contacts, while the last digit seven rotates the wipers into connection with the seventh contact set of the sixth level.

Assuming that the called line is idle the connector completes the connection and signals the called subscriber. When the called subscriber answers the back bridge relay in the connector operates and reverses the direction of current flow in the trunk line leading to the connector. This reverses the flow of current in the upper winding of electro polar zed relay 31 of repeater D. Relay 31 energizes, as the two windings now assist each other, thus closing a circuit for the revers ng relay 2'5. Relay 25, upon energizmg, reverses the direction of the current flow through the calling subscribers battery loop. Th s 1s done to operate coin collectors, call registers, or for other pur oses known to those skilled in the art. pon energizing, relay 25 also operates armature 78 to include the lower winding of impedance coil 33 in the bridge across the talking conductors. This increases the impedance of the bridge and thus cuts down transmission losses.

The release of the connection is accomplished in the usual manner by the restoration of the receiver of the calling subscriber. This allows line relay 30 to deenergize, which opens the bridge across the trunk line conductors 95 and 96 allowingthe connector to release in the usual manner and to remove ground from the release trunk which allows selector H to release and relay 104 of relay set F to deenergize. The deenergization of line relay 30 is followed by the deenergization of all the relays of repeater D that were energized during the conversation. Armature 72 of relay 34, upon falling back, removes holding and guarding ground from test contacts 3, 6, 9 and 12, allowing relay 64 to deenergize and the first selector to release in the usual manner. All the appara-- tus is now ready for another call.

Assuming that the called line is busy, the connector does not complete the connection but sends back a busy signal to the calling subscriber who, hearing the signal, hangs 105 up his receiver and the release takes place in the same manner as if an idle line had been called.

In the foregoing it has been described in detail how the seizure of repeater D from the fourth level resulted in a connection being established from repeater D to selector H. In the same general way the seizure of the repeater D, from the third level results in the establishment of a connection with a selector or other switch connected on the trunk line comprising conductors 177-179, inclusive. When repeater D is seized from the third level, ground is sent from test contact 9 over conductor 53 and through relay completescircuits for relays 111-and 103. These relays operate in the same manner as relays 112 and 104. Relay 103, upon operating, opens the shunt around relay 107 and allows it to reoperate, while at the same time conductors 95 and 96 are connected to conductors 177 and 17 9, respectively. These conductors lead to a switch which,sends holding ground back over conductor 17 8 before relay 103 has had time to deenergize. This ground holds relay 103 energized until the connection is released. It is understood, of course, that the seizure of the repeater in any case results finally in the, operation of relays 34 and 35 in due time to hold up the connection and place a bridge across the trunk conductors 95 and 96. After the connormall nection has been extended to the switch assumed to, beconnected to conductors 17 7 and I to ground. Relay 106, being shorted out in the manner previously described for relays 108 and 107, falls back and'operates re-' lay 102 which connects conductors 95 and 96 to conductors 174 and 176, after which 'the call proceeds in the usual manner. In

case the repeater is seized from the first level relay 61 is energized and places ground on conductor 95 which shorts'out relay 105. Rela 105 upon falling back closes a circuit whic operates relay 101 thereby connecting the trunk line conductors 95 and 96 to conductors 171 and 17 3.

It will be seen that the level from which the repeater is seized determines which switch operates in the distant exchange thus enabling four small and ineflicient groups of trunks to be combined into one larger and more efiicient group, and it will be seen further that a simple and reliable method of ac: complishing this result has been devised, which allows a commercial exchange using such a system to be operated on a more efficient and economical basis.

In the drawing (Fig. 2) the four normally energized relays 105-108, inclusive, are shown connected to exchange battery and ground atthe exchange in which they are located. In actual practice, however, there may be a large enough difference between the battery or the ground potentials of the two exchanges to render the system inoperative. In case such a difference exists or is liable to occur, the two leads 200 and 201 are not conneetedto ground and battery in the same exchange, as shown, but they are instead run over to the exchange in which the relay set E is located and there zomiected to ground and battery, respecive y.

In the foregoing-the trunk line comprising conductors 95 and 96 has been assumed to have access-to four "selector switches. However,' it may be desirable to have 'the apparatus give access to an operator when seized from one of the levels, m which case the corresponding trunk line leading from relay set F connects to an operator instead of a selector. Many other modifications will present themselves to the mind of one skilled in the art and can be made without de arting from the spirit of the invention.

aving described my invention, what I consider to be new and desire to have protected by Letters Patent will be pointed out in. the appended claims.

What I claim as my invention is:

-1. In a telephone system, a trunk line, a source of current, a pair of relays connected in series with each other and said source of current, a second pair of relays connected like the first, a connection from the junction of the rela s of the first pair to one conductor of sai trunk line, a connection from the junction of the second pair of rela s to the other conductor of said trunk km, a plurality of other trunk lines, an individual connecting relay for each of said other trunk lines, means to connect veither pole of said source of current to either conductor of said first trunk line to shunt either relay of either pair to cause it to deenergize, and means controlled by the deenergized relay for closing the circuit for a connecting relay to connect one of said other trunk lines to said first trunk line.

2. In a telephone system, a trunk line, a source of current, a pair of relays connected in series with each other and said source of current, a second pair of relays connected like the first, a connection from the junction of the relays of the first pair to one conductor of said trunk line, a connection from the junction of the relays of the second pair to the other conductor of said trunk line, a plurality of other trunk lines, means to connect either pole of said source of current to either conductor of said first trunk line to shunt either relay of either pair to cause it to deenergize, and means responsive to deenergized relays for connecting said other trunk lines to said first trunk line, the particular one of said other trunk lines that is connected to said first trunk line depending upon which relay is shunted.

3. In a telephone system, a trunk line, a plurality of other trunk lines, a source of current having one pole grounded, means H to connect either pole of said source of current to either conductor of said trunk line,

and means resfponsive to the connecting of said source of current to.

either pole 0 either conductor of said first trunk llne to selectively connect said other trunk lines to said first trunk line. Y

4, In a telephone system, a trunk l1ne, a plurality of other trunk lines, normally disconnected from said first trunk line, a source of currenthaving one pole grounded, means to connect either pole of said source of our-- rent to either conductor'of said trunk line,

deenergization thereof for connecting the associated branch to the said trunk line.

6. In a telephone system, a trunk lme having two branches at one end thereof a relay associated with each branch, the said relays being connected in series with a source of current and being normally energized, a connection from the junction of said relays to a conductor of said trunk line, means at the other end of said trunk line for selectively changing the potential on said conductor to cause either of said relays to deenergize, and means associated with each relay and responsive to the deenergization thereof for connecting the associated branch to the 'said trunk line.

7. In a telephone system, a trunk line having two branches at one end thereof, a rela being connected in series with a source of current and being normally energized, a connection from the junction of said relays to a conductor of said trunk line, 'means at the other end of said trunk line for shunting either of said relays to cause its deenergization, and means associated with each relay and responsive to the deenergization thereof the associated branch to thefor connecting said trunk line.

8. In a telephone system,atrunk line having two branches at one end thereof, a relay associated with each branch, the said relays being connected in series with a source of current and being normally energized, a connection from the junction of said relays to a conductor of said trunk line, means at the other end of said trunk line for extending a connection thereto over either of two different-routes, means for altering the potential .on said trunk conductor in accordance with the route used to. cause the deenergization of one or the other of said rela s', and means associated with each relay an responsive to 70 the deenergization thereof for connecting the associated branch to the said trunk line. In a telephone system, a trunk line having a plurality of branches at one end thereof, a pluralityjof normally energized relays, 7

one for each branch, means atthe other end of said trunk line for selectively controlling said relays over the trunk line conductors to cause any one of them to de nergize, and

means associated with each relay and responsive to the deenergization thereof for connecting the associated branch to the said trunk line. 1

10. In a telephone system, a trunk line having a plurality of branches at one end 35 thereof, a plurality of normally energized relays, one for each branch, a plurality of incoming branches at the other end of said trunk line over which connection may be extended thereto, means effective durin the establishment of connections for selectively deenergizing said relays in accordance with the incoming branches in use, and means associated with each relay and responsive to the deenergization thereof the associated branch to the 11.. In a telephone system, a trunk line having two branches at one end thereof, a relay associated with each branch, said relays being connected in series I of current, a connection from the junction of said relays to a conductor of said trunk line, means at the other end of said trunk line for selectively controlling said relays over said conductor, and meansv controlled by each relay for connectingv its associated branch to said trunk line.

12. In a telephone system, a trunk line having two branches at one end thereof, a

y relay associated with each branch, said relays associatedwlth each branch, the sald relays b eing connected in series with a source of current, a connection from the junction of said relays to a conductor of said trunk line, means at the other end of said trunk line for extending connection thereto over two diff ferent routes, means for selectively control- 1mg said relays over sald conductor 1n accordance with the route muse, and means controlled by each relay for connecting its the outgoing branches and controlling the connection thereof with the'trunk line, and

means associated with the incoming branches for selectively deenergizing said relays;

14. In a telephone system, a trunk line, a

normally disconnected branch extending to for connecting 95 said trunk line.

with a source an automatic selector switch, a relay controlled overa conductor of said trunk line, a slow acting relay and a circuit therefor closed b said first rleay, means controlled by said s ow relay for connecting said branch and for opening the controlling circuit of said first relay, a holdingcircuit for said slow relay, and means in the said selector for closing said holding circuit to maintain 10 said slow relay energized.

15.-In a telephone system, a trunk line two normally energized relays at one end oi said trunk line connected in serieswith each other and a source of current, means for connecting with said trunk line at the other end over two difierent aths, and means res naive to the establis ent of the connectlon for shunting one of said relays to allow it to de-energize, the relay shunted depending on thepath over which the connection is established.

Signed by me at Chica 0, Cook County, Illinois, this 11th day of ov., 1920.

OHN ERICKSON.' a 

